Frequency-modulation recording and reproducing and its combination with a radio receiver



Nov. 22, 1949 w. v. B. ROBERTS 2,488,936 FREQUENCY MODULATION RECORDING AND REPRODUCING AND ITS COMBINATION WITH A RADIO RECEIVER Filed Dec. 12, 1940 2 Sheets-Sheet 1 Fly.

1454C MIVC'E 71/55 CIRCUIT /ck-z/p 17 8 /9 20 2/ I I 11 13.

I4 3 A MP1 lF/ER DISC'R/M/IVA 70k 4 F.

DETECTOR AMPL/F/ER 1e Ffg. 3

' FREQUFA/C) FREQUENCY CONVERTER) D/V/DPR) MULT/P/L/ER C'ONVE/jTER AMPLl/F/ER HECOR/DER 20 I 22 D/SCR/MINAm/Z I. RAM/ L.) L/M/ZFR DE/TEC'TOR 2.9

23 24 25 26 27 28 (t j R. F. CONVERTER 37-8 AFAMPL. LS. AMPL. OSCILLATOR AMPLIFIER FREQUENCY CUNVERTFR INVENTOR Ml/U P R wan-R VAN 5. ROBE/77$ ATi'oRNEY Nov. 22, 1949 v, ROBERTS 2,488,936

FREQUENCY MODULATION RECORDING AND REPRODUGING AND .ITS COMBINATION WITH A RADIO RECEIVER 2 Sheets- Sheet 2 Filed Dec.

MECHANISM I CONVERTER AMPZ/F/ER RECORD/N6 REAC'MA/CE 050/1 7085 C'lRCU/T 7'0 AMPL/F/ER INVENTOR WALTER VAA8.R08EKTS ATTORNEY Patented Nov. 22, 1949 LATION RECORDING AND aeeaonccmc AND ITS COMBI- FREQUENCY-MODU NATION WITH .of Delaware A RADIO'IRECEIV ER :Walter van B. Roberts, Princeton,

to Radio Corpm-ation of America,

N. 'J.,- assign'or a corporation Application December 12, 1940, Serial No. 369,829 22 Claims. .(Cl. 179100.11)

The present invention relates 'broadly to recording and reproducing systems and more particularly to the recording of soundor other signals in the form of a timing modulated high frequency wave; that is, a high frequency wave modulatedin phaseorfrequency, in accordance with the signal wave form, or a voltage derived therefrom.

In the present specification the term timing modulation will be used to designate either-or both phase modulation and frequency modulation. Accordingly it is to be understood that when either of the terms 'frequency modulation or phase modulation is used the other is not excluded since it is a well known fact that either type of modulation maybe used with the same result as the other by suitably altering the frequency characteristic of the'modulating voltage of one with respect to that of the other.

The present invention has for one of its objects to provide a-system of recording'and reproducing which possesses substantially the same advantages as are obtained in frequency modulated radio transmissions, and in addition other advantages which are of'particular interest and importance in the recording and reproducing art.

Thus, among the objects of the present invention is the provision of a phonographic system capable of wide dynamic range, increased length of playing time for any given size record, and greatly reduced incidental" noise background.

In the usual methods of recording now prevalent, the requirement of recording accurately various wave forms having a wide frequency range and a large amplitude range, is so severe that ideal operation is by no means secured. For example, for high fidelity work, the vibration of the recording needle must have a smooth frequency characteristic over the entire range of audible frequencies; namely, a range of some 300 to l, and in addition the reproducing pickup must have similarly excellent characteristics over this wide range. With equalizer systems, as in use at present, the desired over-all faithfulness of reproduction can only be approximated and then only with considerable loss in efiiciency, both on recording and reproducing.

Again, in order to maintain a good ratio of desired signal to surface noise, it has been necessary to reduce the dynamic range of musical recordings in order .to prevent overloading thesystem during. loud passages on the one hand, and on the other hand to assure that during In accordance of the above mentioned drawbacks of present accordance with the instantaneous potential of the signalling wave itself, or of a voltage derived therefrom.

presseduponthe modulating system.

Continuing on the assumption that a frequency modulation is used, a system incorporating certain of the features of the invention might be as follows:

Audio signals to be reproduced may be first passed through any desired arrangements for pre-emphasizing certain frequencies (if this is desirable) or for expanding or compressing their dynamic range. The resulting energy which is herein called the modulating potential, is then used .to modulate a source of superaudible frequency, which may have a mean frequency of 50,000 cycles, for example. Themaximum modulation voltage might be arranged to cause the instantaneous frequency to swing as high as'80,000 cycles-or as low as 20,000 cycles. This constant amplitude frequency modulated wave isthen impressed upon a piezo-electric crystal, Whose natural frequency is'preferably above the highest frequency "to be recorded, and the vibrations of this crystal are imparted to a suitable recorder of cutting or formed within the groove by a crystal-driven, rounded-point, embossing tool. In such an ar rangement since the embossing is within the groove, the embossed track is out of harms way. In still another arrangement contemplated by the present invention, a cutting or embossing tool is used which preferably vibrates up and down on the blank record thus producing a record of the type known as hill and dale.

In such an arrangement the embossing may be performed within a previously prepared groove in which case the cutting or embossing tool is guided by the groove, or the embossing may be performed on the land" of a record with a previously prepared spiral groove. In the latter case, the groove may be used in conjunction with a groove follower associated with the embossing tool to guide or feed the embossing tool along the land of the record.

One of the above noted advantages of the present invention becomes immediately apparent since the combination of hill and dale recording in a system wherein the amplitude of vibration is substantially constant, permits a great increase in the number of lines per inch. It has been found that a line density of the order of 500 lines to the inch is readily possible. This means that a twelve inch record would pla for more than minutes at '78 R. P. M. (revolutions per minute) without using as much as the outer 3 inches of radius. It may be noted in passing that with the particular frequency values given above as illustrative, the longest wave length that will be engraved on the record will occur when the instantaneous 20,000 cycles at the outer portion of the record, and this wave length will be about two and onehalf thousandths of an inch, while the shortest wave length will result from an instantaneous frequency of 80,000 cycles, occurring in the inner portion of the record, and will be about one-third of a thousandth of an inch. Such minute wave lengths might not be feasible to record or reproduce with a system required to function over the wide percentage range of frequencies and amplitudes that is met in present day practice, but it is perfectly feasible where, as in the present invention, the percentage range of frequencies is so greatly reduced and the amplitude is substantially constant.

. While a constant amplitude has been referred to above, what is meant in that no attempt is made to vary the amplitude. As a matter of fact even if the cutting stylus, or reproducing arrangement has an inherent tendency to operate more efficiently at one frequency than another, it will make little or no difference in the final result because in accordance with the invention the reproducing circuits, as will be seen hereinafter, include limiter devices for nullifying the effect of amplitude variations.

In reproducing from a record produced in accordance with the invention, a crystal pickup device may be used operating similarly to the recorder, and this pickup device will then pick up mechanical vibrations which it transforms into electrical energy in the form of a frequencymodulated, super-audible frequency voltage, whose amplitude is more or less constant. If the amplitude of this voltage varies considerably with frequency it may be passed, if desired, through corrective networks for restoring it to more nearly a constant value, but in any case, after sufficient amplification it will preferably be passed through a limiter stage for removing substantially all frequency has dropped to;

amplitude modulation. Following the limiter there may be provided the usual type of frequency modulation discriminator detector, or preferably, in view of the relatively low frequencies involved, the limiter may be followed by a detection system similar to that described in my co-pending United States patent application, Serial No. 354,982, filed August 31, 1940, now Patent No. 2,286,377, granted June 16, 1942.

The present invention also provides for producing a record of the type described, by a meth- 0d of slow speed recording. One way in which this may be accomplished is to first make a rec- 0rd of the audio-frequency of the conventional type but with highest possible fidelity and then playing back this record at a slower speed. The reproduction from this playback or a voltage derived therefrom is then used to frequency modulate a wave the frequency of which is reduced from the desired'carrier frequency in the same proportion as the above mentioned playback speed was reduced from the recording speed. The resulting frequency modulated wave is recorded on a record which is runnin at a speed which is reduced from the desired speed of reproduction in the same proportion as the above mentioned carrier was reduced from the desired carrier. In reproducing the last mentioned record, the record is run at the said desired speed of reproduction.

The present invention also provides an arrangement for recording frequency modulated signals picked up by a frequency modulation receiver.

Assuming that such a, receiver is provided with a radio frequency amplifier, a converter including an oscillator, an intermediate frequency amplifier, a limiter, a discriminator-detector, an audio-frequency amplifier, and a loud speaker, then the output of either the intermediate frequency amplifier or the limiter is converted to a suitable intermediate frequency and passed through a frequency divider thereby reducing both mean frequency and frequency swing to proper values for recording. The energy may then be amplified and fed to the recorder mechanism and impressed upon a record as heretofore mentioned. If, as may happen, the intermediate frequency swing referred to above cannot be directly subdivided to the proper recording value, it may be necessary to use a frequency divider in combination with a frequency multiplier. It is obvious from a mathematical standpoint that by properly combining frequency conversion, frequency division, and frequency multiplication, substantially any combination of mean frequency and frequency swing may be obtained. Once the desired swing is obtained, additional converters may always be utilized to convert the energy to the proper mean frequency after which it is amplified and fed to the recorder.

Another feature of the present invention is the provision of means for reproducing records made in accordance with the invention through a frequency modulation receiver. In such a. case, a suitable pickup is used for picking up the energy from the record as previously described and its voltage fed through an amplifier and then through a frequency multiplier and a converter in order that the energy may be converted to energy of a mean frequency and a frequency swing which correspond to the frequency and band width respectively of the intermediate frequency amplifier of the receiver. When such energ is obtained it may be fed into the input of the 5;; receiver intermediate frequency: amplifiers from which it is; passed; thro gh. the limiterr thence through the; discriminatbn detector; thence through the a audio frequency; amplifier? and last-- ly impressed upon the loudspeaker.-

It is appreciated that the: inventionma-y bezused, in conjunction withfiaconstant linear: speed type of disc. drive in order that=thewaves may. be-kept. uniform. throughout: the portion of ther disc used; Also, the spiral groove; on; the!" record may be used-for guiding purposesponly on both recording; and playing back in which case'the:recordingalsz" put-on the land.

Among other objects oi the invention are the provision of photo-electric pickup means arranged; to respond to light reflected from: the; land? of" thesrecord for reproduction-of therecorded. sig;--- nals.

While the invention. will: be; described inncon nection with discrrecords. it=is not intended -to=be limited thereto .since other: types of I records may-- be; used. In other words, it: should be distinctly.- understood that the inventionf maybe practiced equally well With-other types ofrecords which may include amongothers: magnetic type records; photographicon film, type: records,:.recordsmade. by. cutting'through anopaquelayeron filmor by embossing. on film, recordsi whichemploy-variable pressure ona conducting; pickupin order to.-pro-- vide for: varying contact. resistance; Such. a variable contact resistance: may: be provided also I by the. intermittent-interruption of: a-circuit by vir-- ture' of the failure of; 'thewpickup needle to follow' exactlya-hill anddale record track. This would.

occur for instancewhen theipickup needle fails-t dip into :the dalef but instead jumps: track.

The novel features which: are. believed to becharacteristic: of the: invention are set forth in particularity in the appended claims. Themventionitself, however; .as to both its organization and method of operation will best be understood.- by reference to the following; description :taken-in; connectionawiththefdrawingzin which-there have been indicated diagrammatically.- several-:orga-ni zations whereby the: invention may. be carried: into effect.

In the drawing, Figure l is ta diagramm'aticarepe' portions: of :the record track. from. hill. to hi1l: of the;

resentati'on of-a circuitsorganization.and recorder; I

unit which may be: used: for producing records, in:

accordance withthespresent inventionyFigurel is a diagrammatic representation of a suitable circuit and pickup means which may be used for reproducing -theirecorded'signalsi; Figure 3illustratesin diagrammatic form a frequency-'modu.--- lation receiver with;circuit arrangements forire producing and makin'g recordsi in: accordance with: the present' invention;Figures 4A and'4B dialgrammatically represent an arrangementcwhich: may-be used for reduced speedrecording; .Figure 5 4s azsection through a record'. perpendicular to a radius of the disc showin'gthe land? andaa: portion of the embossing tool"; Figure 6"is a crossisection of the recording disc: along, a diameter thereof, the discbeing'of 'thetype where. the; groove is used'as a; guide forzthep'ickup devicei or embossing means; and, Figured illustrates an: arrangementusing reflected light from the land. of the record-for reproducing the signals.

Referring more particularly to Figure. l of the. drawing, I6 is a motor for driving a-turnsta'blezr l3 through reduction gearingv I 5? and shaft. or spindle [4. A record i2: is shown on the turn:- table with: the spindle; I4 passing through am 77'5 modul ation, detectediin: a: discriminato openingeimthe; recordasuitabl r and arranged so: as tozprerent slippage. The record |;2::is si1own.. being: cut or:- embossed; by; tool;v lzls' which". is driven, by 4 a piezo 'electrirr crystal;- 8-. The: tool; is: mounted on the crystabih anyrsuitable manner; In this way, the motion of 1 theikcrystal: trans f erred to the 12001: movina: it uni-and; down: and; thereby embossing; or: cutting-:1 the record; track;- accordingly.

WhiIe-a-crystal hasebeem-shown as :the drivingi means: for the took-I 1;; itsis to, beunderstoodzthat, other'typ'es of drivers may be-used-suchasan; electro-magnetic: driven,v Crystal 81 is; mounted? between plates 9 andl1 and-the: driving voltage is impressed betweencthe plates: S -and l0.

Amodulatingmotential derived fromvthens'ignal, to be recorded isimpressedsacross terminals land; 2. and thereby fed to acreactance tubercircuit which acts: to frequen'cysmodulateethe oscillations: produced;- by oscillatorv 4- in. accordance-withthe modulating potentiali To: obtain suitablylarge frequency variations, its is preferable to:'Inake:-the? mean frequency" generated by; oscillator 4- higher than the, mean: frequency; which iszt'o be used-ion the actual-operation ofthe embossingitool or cutten. Accordingly; the frequency modulated output of" oscillat0r4 is fedto aconverter; circuiti wherein the energyis-converted to. lower frequencies: The.- output; of. thevconv'erter: preferably amplified.

.- in a suitable wide'band amplifier 5 which-may take; the form 'ofg thex amplifier illustrated 'in Figure; 410i UnitedState's-Batent No. 1,925,340. The output of amplifier? 6 isr then. impressed between previously; mentionedipl-ates' or, electrodes r 9 and-v III" of; crystal 8; Thus; the crystal 8- movesaccordancezwith the outputyoltageof:amplifier 6;

To play back: therecord [:21 after the desired signals, are'recordedthereon-, .a system like that. shown in, Fig,ure:-'21 may. beused-l In-FigureZ; as? in Figure 1; a;:turn.- table:- l:3--isdriven: by I a motor: through gear reduction means l5. and: shaft. or: spi'ndle I 4-. The record i2 is placed ontheturm table |3with its centralropeningregistering with spindlel4 inztherusual'm'annerw As.the record?- is rotated the pickup 11 travels along the-spiralgroove-andrthe vibrations imparted to pickup. IT

by the waves-on thaerecordare: transformed into-.- electrical energy; If; ascrystal-pickup is; used,- the: follower or needle: acts? to variably deform the.

crystal in accordance with the recordedmatterr The: electrical energy is preferably amplified in an amplifier' l8ia'ndi then: fed to a discrimiriator-detector l 9 oflanysuitabletype from which; the: audio: signals arerderived. After: amplificai tionvin' -an'xamplifier""20ithe. audio-signals are fed:

to ai-loud speakerrll; in' -the usualma-nner.

If. itiisadesiredtl'to make; records; or theztypeiclescribed "herein; from broadcastsreceived by a frequency modulation rec-eiver, or if; it iscdesired to" play back records: produced in accordance. withv the present:invention through. a frequency; mod:-- ulation receiver designed for radio reception; an: arrangementsuch asfshown'rschematicallyin Figur'e; Bsmay, be used'u. InFigure'BL. elements 22 through 19 :are: intendedtomepresentzin a general waythe construction of. a stan'dard frequency? modulation receivcri'ofithe type which: is nowcommercially"availablefor radio reception In such a receiverenergy picked up by antenna 22 is amplified in a: radio: frequency amplifier 23; converted into a suitabledntermediate. frequency, in a converter-oscillator 2'4, amplified; in a suite able'intermediatesamplifien'zii,1 treatedin a'limiter. 2-6i'in ordertto remove; any"existinggamplitude det'ecton 7 21, amplified in an audio frequency amplifier 28 and fed to a loud speaker or other translator 29.

While it-may be possible to record the intermediate frequency output of the limiter 26 directly by impressing the output voltage of 26 across the two plates 9 and ID of a crystal recorder such as shown in Figure 1, it will be found that the frequencies involved are usually too high and the frequency swing too great for efficient recording and reproduction. Accordingly, the present invention provides a novel energy conditioning circuit which may be interposed between the limiter 2S and a suitable recorder 36 for reducing both frequency swing and mean frequency. A suitable conditioning circuit may comprise a combination of one or more converters, one or more frequency dividers and one or more frequency multipliers arranged in any suitable manner to provide any desired mean frequency and any desired frequency swing for efficient recording. One of many possible arrangements has been illustrated in Figure 3, wherein the output of limiter 26 is fed to a converter 31 through switch 3% (when closed) for frequency reducing purposes. Of course, while a converter such as 31 takes care of frequency reduction, it cannot reduce the frequency swing. To reduce the frequency swing, the energy from converter 3| is fed to a frequency divider 32. Frequency dividers capable of dividing by any desired divisor may in some cases be difiicult to construct, so that in accordance with the present invention the effect of dividing by a suitable divisor is obtained through the use of a suitable combination of frequency dividers 32 and frequency multipliers 33. One or more additional converters may be desirable for frequency reduction in several steps in order to simplify the frequency swing reduction. In such a case one or more suitable converters such as 34 may be provided. It is obvious from a mathematical standpoint that substantially any desired frequency and frequency swing may be obtained by properly combining frequency conversion, frequency multiplication and frequency division.

After the energy is converted to the proper frequency and frequencyswing, it may be fed to the recorder 36 through an amplifier and recorded on a suitable record such as the disc i2 shown in Figure 1.

From the preceding matter, it can be seen at once that a record prepared in accordance with the present invention cannot be played back efficiently through .a standard frequency modulation receiver bysimply impressing the voltage picked up by a pickup, as for instance that shown at IT in Figure 2, directly upon the input of the intermediate frequency amplifier of the receiver shown in Figure .3. The reason for this is that amplifier 25 is ordinarily designed for operation at much higher frequencies than are picked up from the record. Also, frequency modulation receivers are designed for greater frequency swings than those on the record. Accordingly, the output of the pickup 41 should not only be converted to higher frequencies but in addition its frequency swing should be increased. For this purpose the invention provides a circuit arrangement intermediate the output of pickup 4i and the input of intermediate amplifier 25 which conditions the energy picked up by pickup 4| for proper and efiicient handling by the frequency modulation receiver. A suitable circuit for this purpose may comprise an amplifier for amplifying the voltage picked up by 4|, a frequency multiplier 39 for increasing the frequency swing to the desired value and a converter 38 to convert the mean frequency to a value suited to amplifier '25. The output of the converter 38 is fed to the input of intermediate frequency amplifier 25 through a suitable switching means 31.

It may sometimes be desirable to produce a record of the type described herein with ordinary cutting equipment; that is, equipment which is designed for operation at the usual audio-frequencies. In such an event, the present invention provides a system of slow speed recording which may take the form shown schematically in Figures 4A and 413. Since in slow speed recording everything must be slowed down proportionately in order that the record when played back at the usual speed will provide faithful reproduction, it is necessary to, so to speak, slow down the audio-frequency. One feasible method of doing this is to record the audiofrequency derived from a device 42 which may be a microphone, onto a record 12 in the usual manner, as indicated in Figure 4A. In other words, the audio-frequency output of 42 is amplified in a suitable audio-frequency amplifier 43 and the resulting voltage impressed between plates 9 and I0 of crystal 44. Crystal 44 is then used to drive a suitable cutter which cuts the record I! in accordance with the audio-frequency voltage impressed between plates 9 and 10. As in Figure 1, the record 12 is placed on a turn table l3 with its hole registering with spindle 14 as is usual. The turn table I3 is rotated by means of motor it through reduction gearing l5 similar to the arrangement shown in Figure 1. The record l2 may then be placed on a reproducing turn table 50 (see Figure 4B) which may be similar to the turn table 13 of Figure 4A except that motor 5! drives turn table 50 through reduction gearing 52 and spindle 53 at a much lower speed than that at which the record was made. i

' A pickup 45 is used to pick up the signals from the record l2 and to feed them to a reactance tube circuit 46 similar to the reactance tube circuit 3 of Figure 1. The reactance tube circuit 46 is used to frequency modulate energy generated by oscillator 47, and this frequency modulated energy is converted in 48, then amplified in 49,

and applied to recorder 54. It is to be understood, however, that the mean frequency of the waves applied to 54 is reduced from the value to be yielded by the record in normal use in the same proportion as the speed of turn table 50 is reduced.

In playing back a record made by the recording mechanism 54 it should be run at its normal speed. In other words, such a record may be played back by either of the systems shown in Figures 2 and 3 without altering the record driving mechanisms thereof.

- Comparing the arrangement shown in Figure 43 with the arrangement shown in Figure 1, it should be noted that assuming that the turn table 50 of Figure 4B is operating at /th the speed at which the record is to be played back in a system such as shown in either Figures 2 or 3, then the mean frequency of waves impressed on 54 is /1lth of the frequency of the waves impressed on tool H of Figure 1. Likewise, the turn table associated with recording mechanism 54 operates at /nth the speed of turn table l3 shown in Figure 1.

In the foregoing description, for the sake of 'definiteness, a disc recording system was de- 1 scribed for the recording and playing back at reduced "spee 3 the ophonea2.

signals originatin .-1 at *However -inasmuch any perfection whiclr may occur duringthis intermediate stage of the conventional =recording-an-d "reproducing in fashion will-be evident in the ii final I frequency :modu-lated 1 record; 'itwould be preferable to use of the signals a p for this intermediate handling hotographic' film type or-record arranged to operate at a-sufiiciently high linear speed soas to-"prducethe highest pos'sible-fidel- *ity and lowest possible background noise.

At this epointonemight well inquirewhether -there is any reasonron producinga frequency modulated reco :c' ma'k ing this re rd at all if, in" the processof That perfect record can be made,

whyishould noii'it ora copy thereof ibe played backin the conventional-manner by the ultimate user of the record? Thelanswen-to this questiorris' "that while substantially perfect recording and" reproduction 'may be possible in the: laboratory andinconelection with L bulk of such wthe' system as-above described; the

l the equipment for playi-ngit back with high 1 by the 'ordin fidelity is such as to make it impracticalfor use Such equipment; however,

ary user.

is justified as a .step' in 53, manufacturing process I for producing: -a; =largenumber*of :copies of the V ultimate frequency modulated product adapted I for use by the ordinary user.

' Another type iof 'recofrding whichmay be used wherein the: record I 2,

thereof, 'iscomposed of a light reflectingrmaterial. :order to reproduce "from such a record;

a "source "of light 60 is ar- :rangedso 't'hatnthelighttnerefrom passes through an optical system including lens BI and as indi- :whichxmay thus bylzamropening..;622iof reasonable size ThefSiZeTUftillh opening is such that trictcell 64 receives the'light reflected oint 'on :thdrffland. 1:." In iother' words, tions a single :In :the earrangementillustratedgttheYaIm :63 also acts. as the guiding-means for'theisourceof light, itrbeing noted that the end thereoftcooperates;with the'record groove to feed the source for light and photocell. acrossx-the'frecord. .The output of the shownin Figure wwherein, there is.illustrated'-6 Figure 2 or'amplifier lllshownsin-Figure 3 of the- :photocell may-ulce impressed-upon the input of a suitable amplifier such as amplifier 8 shown-"in .Hin the manner set :forth in; either of? said Figure I 2 and 3.

A preferred, type of 1 cutting; or embossing tool a section of acrecord 1| ZAgreatly. enlarged). in- .the

processof beingcutorehrbossed by means of tool ...t0ol IL is shown. ..s-hould fbee-unders .either cutting or ,I lrwhichoisbeingdriven bye crystal 8. Whilepthe as. having. a rounded point, it tood that it .may ,be shapedlofor embossing depending upon the typeof recording preferred. Any. suitable .ar-

trangement, for :holding the tool I I .in place may betused. One such arrangement may comprise "which acts to hold the tool ll tightly in its receptacle. The portion 56 of the '-'la'nd is the part whichhas been'embossed or z' along the hea er "out while :portior'f51 shows the uncut portion. in Figure 6; ai pickupl I- is shown being'giiided the record 'li by means ofa cord; 'a:s=ubstantially perfect record of the ordinary'type'has-to be 1 made. is", if a substantially a record-and the great expense of groove follower 58 the -point i -5 9 "of which -is -='-adafpted to fit into the-record groove. Follower 58 may be attached-to thewcrystahcarrier Thin any suitable manner as by meanspf a-suitable 5 resilient mounting means 10.

' It is to be understood that a variable resistance or capacity typepickuparrangement may be used if-desired. 111 0118 81101 arrangement the land of a hill and dale (preferably conductive) l0- reco'rd inaybeused as one-plate of a condenser rin which ease a suitable condenser electrode -Which:isguided just abov'e' the lan'd by a guiding 5; means working in co n-junction with the 1 grooveas sh'own in Figures fiend" 7 forms the -other conndenser platet ff-Ilhe varying 'distancebetweenthe guided plate and the; landiflprovidesa'variable .izcapacity which may bezsconnected vin series with atsource -ofs.currentvandt an impedance element to. form a: series'sicircuit. 'Rotentialsvariations across :the. impedance elementtmaysthen. .-be1;-im-

presseduponsthexinput: -oian amplifier ci-rcuit such as shownitat:i I B: .in- Figure 2. Illhe amplified ---:renergyz.mayzthen:-be fed. to.. ah'discriminatorzi deii'tector as invFigure 21in order-tmderive thessignals,

25l z-flnd iafter'; amplification :theizsignalsnnay be fed 1302 a ""loudi-;:speakerzror-- 'zother:zsuitablexutiliZing .vpdevice.

.It will be evidentrthat a mostjmportantzadvan- 1 tagerofzthesystem:ofirecordingandsreproducing herein ldisclosert. is nthat' :=it:: ofiersz. a-::;practical method of editing recorded subjectwrmatter-twithout .1introducingldistortion. It is: sometimes desirable to record-;an-;entire;.programrin iord-er to assure obtaining;v all; the zvarious 1 desired aportions :of the program. While-- editing-i5; possible with present daysrecordingsystems; it is evident -.that-distortion: is introduced in iplayingeback the subject 5 matter and in-r-re-rec'ordingthe desired portions thereof due .to' the difficultyioflfollowing 40;; avcomplex. 'waverformwwitn both? the reproducing pickupsandtherecording. .-too1.- n-With a frequency ?--modula-t'ed= Wave recording of. the type: disclosed herein :suchdistortion-sis avoided?- becausei-the signal energy is resolvedzinto :purely frequency ichanges-of aicarrierwgso thatuthe r recorded fre- .;quency modulated-wave maybe 'derivedfrom the i original record: and -recorded directly :on. another erecord without :the necessitys of -1 deriving; a the "audio-frequencysignals therefrom.

.V/Thile'there :have been indicated and described several, systems-for carrying the-present invenrtion? into efie'ct, Iit wil'l' 'be apparent; to one-skilled in theaart that :t-he;inventio-nigisby. -no.-means limited to'the panticularnorganization 'shown and 7 described but that :many modifications. may be -ma'de without departing :iromthe, scope of the :invention 1 as set. forth ;in the appended: claims.

. Lclaim:

1: 'iIheZmethOdT ofzrecording;audible signals lhich; :comprisesithe;xstepscoiz producing: alter- ;tnating electric 'fin l'- i0f substantially :lconstant amplitude *andghayi-ng. az-means i-frequencyiof ot-he order of 50,000 cycles per second; frequency :modul'ating";s'aidxenexfglc as. aufunction of said Qsign'als :I'iIYGCOI'dil'lgithSl resultant: frequency mod- ;ulatedtenergyion a recording'medium; and'mainstaining i the iratioaof maximum-frequency to min- --imum'-"frequency of said -irequency.modulated 'Jenergy; smallastcomparedzrto the ratio; of'maxi- Imun1. frequencyttto'zminimum frequency of :said signals.

i 2. The; method-r01 ---re'cording --.audio-frequency selectrical:energyrof :variable: intensity and frequency, which? comprises; the steps of; producing alternating: lelexztricalctwaveszzi:of gsuper-audible frequency varying the frequency of said waves above and below a mean value in accordance with the intensity of the audio-frequency energy and at a rate which is dependent upon the frequency of the audio-frequency energy; and recording the resultant waves on a recording medium, the ratio of maximum frequency to minimum frequency of the frequency modulated waves being a fraction of the ratio of maximum frequency to minimum frequency of the audiofrequency energy, and the difference between the maximum frequency and the minimum frequency of the frequency modulated waves being a multiple of the difference between the maximum frequency and the minimum frequency of the audio-frequency energy.

3. The method of recording audio-frequency signals of variable intensity and frequency which comprises the steps of recording the audio signals at a predetermined speed; producing electrical waves of super-audible frequency; transforming said recorded audio signals into electrical signals of lower audio frequencies by reproducing said recording at a substantially lower speed than said recording speed; varying the frequency of said super-audible frequency waves above and below a mean value in accordance with the intensity and the frequencies of the lastnamed audio-frequency signals; and recording the resultant frequency modulated waves on a recording medium.

4. In a sound recording method, the steps of producing audio-frequency electrical energy representing the sound desired to be recorded and later recreated; generating alternating electrical waves of super-audible frequency; frequency modulating said super-audible waves over a wide frequency range in accordance with said audiofrequency energy, reducing the frequency of the frequency modulated waves, transforming the reduced frequency waves into corresponding mechanical vibrations and imparting to a solid recording medium shape undulations corresponding to said vibrations.

5. In a combination radio signal receiving and record transducing apparatus for receiving and utilizing timing modulated carrier waves: a circuit including a converter network to reduce received waves to an intermediate frequency range an amplitude modulation limiter network following the converter; a detection network following the limiter network; and utilizing means coupled to the limiter; said utilizing means including signal recording structure for recording timing modulated waves of lower mean frequency and lower frequency swing; a conditioning circuit coupled to the limiter network for reducing both the frequency swing and mean frequency of the modulated wave output of the limiter to that of the recording structure; and connecting means for supplying the conditioned modulated wave energy to the recording structure.

6. In a combination radio signal receiving and record transducing apparatus for receiving and utilizing timing modulated carrier waves and having a circuit including a converter network to reduce received waves to an intermediate frequency range an amplitude modulation limiter network following the converter; a detection network following the limiter network; and a modulation voltage utilizing network coupled to the detection network; the improvement which is characterized by a reproducing network for utilizing said receiver to reproduce records of frequency modulated super-audible Waves having a mean frequency and frequency swing different from said intermediate frequency range, said reproducer network comprising transducing means for converting the records into said superaudible waves; a conditioning circuit coupling said transducing means to a point of the receiver between said converter and limiter, said conditioning circuit being constructed to conform the frequency swing and mean frequency of the modulated super-audible waves to those of said intermediate frequency receiver.

7. The method of reproducing signals which comprises the steps of producing a first recording of the signals at a predeterminedrecording speed; playing back the produced recording at a speed which is lower than the speed at which it was recorded; using the slow speed play back signals to frequency modulate a carrier frequency wave; recording the resultant frequency modulated energy upon a recording medium operating at a speed which corresponds to the said slow speed play back; playing back the last named recording at a speed corresponding to the recording speed of the first named recording; and deriving the desired signals from the last named play back.

8. In a frequency modulation receiver of the superheterodyne type including an intermediate frequency network, an amplitude limiter and a discriminator-detector network; the improvement which comprises a record pickup, means for translating the current output of the pickup into frequency modulated wave energy having a mean frequency equal to the operating intermediate frequency of said receiver, and means for selectively connecting the output of the trans lating means to said intermediate frequency network.

9. In a frequency modulation receiver of the superheterodyne type including an intermediate frequency network and a discriminator-detector network; the improvement which comprises a record pickup, means for translating the current output of the pickup into frequency modulated wave energy having a mean frequency equal to the operating intermediate frequency of said receiver, and means for connecting the output of the translating means to said intermediate frequency network.

10. A method of recording signals as defined by claim 1 in which the recording is made by imparting to a solid recording medium variations in shape corresponding to the energy alternations.

11. In a recording apparatus for recording audible signals as a series of undulations on a record member from which the signals may be reproduced by interaction of the undulations with undulation-following means without appreciable interference from extraneous noise: electric wave I supply structure for supplying electric waves having a substantially constant amplitude and a frequency of the order of 50,060 cycles per second; said supply structure including modulating means having an input circuit for connection to a source of said audible signals and having an output circuit connected in said structure to vary the frequencies of the waves supplied by the structure, in. accordance with variations in amplitude and frequency of said audible signals for providing substantially constant amplitude, frequency modulated waves having a frequency swing larger than the frequency range of said audible signals;

and recording structure connected to said supply anag am 13. structure for imparting tolaa-solid record member undulatory' changes in shape corresponding to the frequency, modulated wavess 12. The-combination as defined by claim 11 in which. the modulating. structure is connected for varyingthe wave. frequency over a frequency range which is amultiple of the frequency range of the audible signals.

13. The combinationas defined by claiinvlll in which the recording structure includes a record deforming element held for vibration in accordance with thefrequency modulated waves in a direction producing record undulations of varying depth in the record:

14. In arecording apparatus;forrecording audible signals as a series of signal modulated undulations on a record member from which the signals may be reproduced by demodulation from waves generated through interaction of the undulations with undulation-following means, without appreciable interference from extraneous noise: record signal supply structure for supplying readily recordable low frequency electric waves, frequency modulated in accordance with said audible signals; said record signal supply structure including signal input means connected for delivering waves having frequencies higher than said readily recordable waves, and frequency reducing means connected to said input means to uniformly reduce the frequencies of said frequency modulated waves to said readily recordable frequencies; and recording structure connected to said supply structure for imparting to a solid record member undulatory changes in shape corresponding to the modulated waves of reduced frequency.

15. A recording apparatus as defined by claim 14 in which the frequency reducing means includes converter elements for uniformly reducing the wave frequencies by a substantially constant frequency.

16. A recording apparatus as defined by claim 14 in which the frequency reducing means includes frequency divider structure for reducing the wave frequenc es by a substantially uniform fraction of their frequencies.

17. A recording apparatus as defined by claim 14 in which the frequency reducing means includes intermediate record transducing elements connected for making an intermediate record of the audible signals and deriving from the intermediate record, low frequency signals corresponding to said audible signals but with frequencies uniformly reduced to a fraction of the original frequencies of said audible signals; and the record signal supply structure also includes generator means for supplying carrier waves correspondingly lower in frequency than the frequency of the carrier to be reproduced from said record member, and modulating means connected for frequency modulating said carrier waves in accordance with said low frequency signals to provide modulated signals for transfer to the recording structure to make a final recording at a final recording speed lower than a predetermined reproducing speed, from which final recording the desired audible signals can be reproduced.

18. In an apparatus for recording signals as super-audible, frequency modulated undulations in a record medium: first recording means including a recording head and record advancing means for preparing a record of said signals at a predetermined speed of record advance with respect to the recording head; playback means including a playback head and record advancing means connectedtfor transducing; said record to frequency such that when multiplied by the ratio of said first recording speed to said'playback speed itis above the audible range.

19; In an apparatus for recording signals as super-audible, frequency modulated undulations in a record medium: first recording means including a recording head and record advancing means for preparing a record of said signals at a predetermined speed of record advance with respect to the recording head; playback means including a playback head and record advancing means connected for transducing said record to play back signals while the record is advanced with respect to the playback head at a speed lower than the speed of said recording; and second recording means connected for receiving said playback signals and preparing a frequency modulated recording of said last-mentioned signals as physical undulations in a recording medium; said second recording means including supply structure connected to supply for said frequency modulated recording, a carrier wave having a frequency such that when multiplied by the ratio of said first recording speed to said playback speed it is of the order of 50,000 cycles per second.

20. In a signal transducing apparatus having a pass circuit including an input network for receiving frequency modulated waves, an intermediate frequency network connected to said input network for amplifying received waves having predetermined values of mean frequency and frequency swing, and an output network including modulation deriving means connected to the intermediate frequency network for delivering amplified signals corresponding to the modulations of said amplified waves record transducing means connected for transducing frequency modulated records of record signals having predetermined values of mean frequency and frequency swing different from said first-mentioned predetermined values; said transducing means including a record transducing circuit having circuit elements connected for including at least a part of said intermediate frequency network in said record transducing circuit for amplifying said record signals; said transducing circuit including a conditioning network connected for changing the mean frequency and frequency swing of signals in said transducing circuit from one of said predetermined values to the other for transducing records without separately deriving the record signal modulations.

21. The combination as defined by claim 20 in which the transducing means includes recording elements connected for making records of the record signals, and the transducing circuit is connected to receive the record signals from the intermediate frequency network of the pass circuit.

22. The combination as defined by claim 20 in which the transducing means includes record reproducing elements for reproducing the record signals from recordings and the transducing circuit is connected to deliver the record signals to 15 the intermediate frequency network of the pass Number ir u t. 1,917,003 WALTER VAN B. ROBERTS. 1,943,373 1,964,375 REFERENCES CITED 5 2 0 7 429 The following references are of record in the 2,112,010 file of this patent: 2,153,779 2,208,091 UNITED STATES PATENTS 2,241,569 Number Name Date 10 2,230,231 1,481,461 Emerson Jan. 22, 1924 2,304,633 1,548,895 Mertz Aug. 11, 1925 1,603,237 Mills Oct. 19, 1926 1,891,227 Friebus Dec. 20, 1932 Number 1,916,973 Friebus July 4, 1933 16 3731973 Name Date Williams July 4, 1933 Matthias Jan. 16, 1934 Wright June 26, 1934 Crosby July 20, 1937 Brimberg Mar. 22, 1938 Travis Apr. 11, 1939 Zakaria-s July 16, 1940 Zakarias May 13, 1941 Crosby Feb. 4, 1941 Farnsworth Dec. 8, 1942 FOREIGN PATENTS Country Date Great Britain June 30, 1932 

